Correcting a False Assertion About the Internet

The main reason for creating his blog was to correct false impressions and spin about technical subjects with policy implications. It’s common practice these days for folks with a policy ax to grind to argue for it with technical assertions that sound like they might be true but are not, in fact, the truth. During the net neutrality debate a number of claims were made about the Internet that constructed a mythical history, and claims of that kind can be hard to assess, so I’m not sure how successful we’ve been on that front. In the context of spectrum policy, a number of claims have been made about spectrum technology that are a lot easier to assess because we can examine current systems and emerging standards.

Yesterday, some folks at Level 3 published a blog post that appeared to be a deeply technical analysis of the cable modem network, complete with cable modem configuration files, Wireshark traffic logs, and charts and graphs. The post was false and misleading, despite its technical veneer, and transparently so.

The critical issue in the complaints that Netflix has made about Comcast’s treatment of the Xbox is the question of “managed services.” The FCC’s Open Internet Report and Order permits broadband service providers to treat managed services different from Internet access services, and Comcast argues that its Xfinity On Demand is a “managed service,” while Netflix claims that all on-demand video services are “Internet service.”

The distinction is simple to make: if the service begins and ends on the provider’s own network, or on some other network that is not part of the Internet, it’s a managed service. Voice is a good example: Comcast and the other triple play providers (including the other cable companies and the former phone companies like AT&T, Verizon, and Century Link) offer a voice service that connects customers to the telephone network. While there is some IP involved within the provider’s network, and there may be some IP at the other end, this service switches in the middle over the PSTN and uses numbers associated with the PSTN. So it’s VoIP but it’s not an Interenet service. Skype is different, of course, because it’s an Internet application that switches in the middle over an Internet backbone or peering connection.

Before we move on to the testing for traffic that we conducted, we wanted to check to see if the Xfinity servers identified by the IP addresses above are a part of the Internet or if they are truly on a separate private network as Comcast’s statements appear to claim. To do this, we simply went to our work location and used that non-Comcast Internet connectivity to see if we could find those servers on the Internet. We executed a ping command to see if the servers were reachable and would respond. Sure enough they did. This implies that Comcast serves Xfinity traffic utilizing the Internet rather than a virtually or physically private network.

This is novel indeed. The ping command (which sends a message to an IP address and gets a reply) says that the Xfinity server is reachable from the Internet, but it doesn’t verify that it provides services to or from the Internet. In fact, a more serious test would indicate two things:

The Xfinity server on the Comcast network; and

The Xfinity server only provides service to clients that are also within the Comcast network.

They would have used the common “traceroute” command to verify the location of the Xfinity server with IP address 76.96.126.242. I’ve done this from the Comcast network and determined that it’s inside the Comcast net, in Chicago:

Consequently, it’s “on net” for Comcast customers. The example of an Internet Service the Level 3 engineers use is actually “on-net” to them, as MLB is hosted on Level 3 servers, but off-net to all MLB users.

Level 3 clearly understands the difference between on-net and off-net services, as it sells an Extended On-Net service. The pitch for this service includes the following benefit: